Slush pump piston rod packing



1963 A. L. LEMAN SLUSH PUMP PISTON ROD PACKING 2 Sheet-Sheet 1 FiledFeb. 19, 1959 INVENTOR.

ARTHUR L. LEMAN ATTORNEYS Feb. 5, 1963 A. L. LEMAN 3,076,558

SLUSH PUMP PISTON ROD PACKING Filed Feb. 19, 1959 2 Sheets-Sheet 2 INVEN TOR.

ARTHUR L. LEMAN 0 8M7: 7M, M411 '0- m ATTORNEYS diameters.

3,076,658 SLUSH PUMP'PISTGN ROD PACKING Arthur L. Leman, R0. 802124068,Houston, Tex. Filed Feb; 19, 1959, Ser. No. 794,429 1 Claim. (Cl.277-121) This invention relates to reciprocating piston pumps,especially those handling fluids likely to contain abrasive matter, suchas slush pumps employed in the oil fields. More particularly it aims toprovide for such pumps an improved piston rod packing assembly wherebyan eifect-ive seal is maintained despite variations in the piston roddiameter at the packing region such as frequently occurs through wear inthe course of the pump operation.

In the drawings illustrating by way of example certain embodiments ofthe invention:

FIG. 1 is a longitudinal section of a portion of the power end of a pumpcylinder having a stuffing box and packing of the invention operativelyinstalled, the piston rod portion thereat being of initial or normaldiameter;

FIG. 2 is a similar cross-sectional view showing a worn portion of therod at the stufling box;

FIG. 3 is a view mainly in longitudinal section of the power end and anintermediate portion of a pump cylinder illustrating a modifiedapplication of the invention d thereto; and 4 FIG. 4 shows" separatelyin perspective a wedge-ring packing element of the invention.

In'reciprocating slush pumps and others handling fluids containingabrasives the piston rods become worn to a reduced diameter. Thisdiameter-reducingv wear generally is greatest at an' intermediate orsubstantially midlength part of the rod and merges into less worn endportions. If to continue to seal off the fluid effectively the packingmust be appreciably tight when it surrounds the rod section of minimumdiameter. But in the conventional stuffing box it the packing is madesufiiciently tight for a worn rod section, it is subjected to abnormallyhigh compression at the less worn and hence larger rod There being noplace for the packing to escape when entered by a larger-diameter rod'portion, an excessive bearing pressure builds up, causing rapid erosionof the packing as well as further wear of the rod.

In accordance with the invention provision is made for relative reliefof the packing at the largerrod portions while at the smaller sectionssealing engagement with the worn rod is maintained. The two conditionsa's referred to will be apparent from a comparison of FIGS. 1 and 2. InFIG. 2 the packing is-seen sealingly engaged with a worm rod section. Atothertimes in the operation, as at the end of a stroke, with a rodportion of normal or less worn and larger diameter at the stuffing box,the

packing elongates axially as represented in FIG. 1. The

dotted line in FIG. 1 shows the corresponding outline of the packingelement under the condition such as in FIG. 2. I

Referring to the drawings in more detail, in FIGS. 1 and 2 thereciprocating piston rod is indicated at 5, extending through a portionof apump cylinder wall 6 at the power end of the pump. The adjacent endof a housing for the outwardly extending part of the piston rod 5, thatwhich connects to the cross-head (not shown) is designated at 7. Thecylinder wall 6 is apertured for reception of the piston rod stuffingbox designated generally at 10. It will be understood'that the pistonend of the rod is toward the right in FIGS. 1 and 2, similarly as shownin FIG. 3 where an additional length of the pump cylinder appears,containing a piston 8 on the rod 5 and within a cylinder liner 9.

The stuffing box 10 of FIGS. 1' and 2 comprises a generallycylindrical-body 11- having at the outer end an external circumferentialmountingfia'nge 12 and at the op-' posite or inner end an internalflange or annular shoulder 13 surrounding a central aperture dimensionedfrom free reciprocating passage of the piston rod 5 through it.

In the example of FIGS. 1 and 2 the stufilng box as so far described isconventional. The-bore 14 of the stuffing box body 11 is cylindrical anduniform from the outer end at the mounting flange 12 to the inner wallat the annular shoulder 13. It is of adequate diameter to afford thedesired annular space or recess between the box wall and the particularpiston rod which it is to be employed. The box 10 is anchored on thecylinder wall as by studs 12 through the mounting flange 12.

Under the invention such uniformly bored stufiingbox is novelly adaptedfor cooperation with a wedge-ring packing element of the invention to befurther described; see FIG. 4. For this purpose inclined wall means 15is provided that is carried internally by the stufiing box. Such wallmeans 15 in this instance comprises a separate metal or other rigidsleeve insert having over a major portion of its length an outerdiameter for seating lit in thestufling boxbore 14, with the inner endof this boremodifying sleeve 15 abutting the annular shoulder 13 at theinner end of the box 10. p

The inner circumferential wall at the bore of this sleeve 15 is formedalong a'shallow incline over a major portion of its length and at asmall acute angle relative to the axis of piston rod 5. Such angle ofwall inclination'is in the acute range of about 8 to 15, being'appioximately 11 in the illustrated example. Th'us in'efi'ect there''is provided'a gradually inwardly tapering wall" 16- for-die stuflingbox bore, extending toward the inner end of the box and terminating in arelatively short cylindrical-wall portion 18. At said inner end theminimum" bo'r'e' diameter of the box sleeve 15 is still substantiallygreater than the maximum diameter of the piston rod 5 so as to provideannular space between the sleeve 15 andthe rod '5, as designated at S,S.

For cooperation with the inclined-wall means 15 of the stuffing box, andwith the rod 5, the novel packing proper comprises an annularsleeve-like body or ring 20 of rubb'erous or like elastometriccomposition of substantial resiliency and capacity toexpand and contractand in ef- 'fec;t to fiow under application of ex'ternalforce and"resiliently to return toward normal free shape and dimens'ion uponrelease of such force. Noting FIG. 4 as well as the others, this packingring 2%} in longitudinal section is of predominant wedge form. It has anouter wall 21 molded to taper inwardly over a major axial extent of thepacking from a point beyond mid-length toward the outer end 22 andcontinuing to the inner end 23, in conformity with the degree of inclineof the stuifing box inner wall means 15, Le. at an approximate angle of11" to the piston rod axis in the given example. While in some instancesthe packing taper at 21- may begin at or substantially at the outer end22 of the packing ring 20 preferably a relatively short outer endportion 24 is made cylindrical and of a diameter to seat snugly in thebore 14 of the stuffing box 10.

The described structure presents an inwardly tapering packing recess inthe stufiing box 10, defined at the radially outer side of the packingby an outer end portion or the stumng box bore 14 and the inner wall 16;18 of the stufling box sleeve 15, and defined at the radially inner sideof the packing by the piston rod 5. The inner end wall of this packingrecess is defined by the internal annular shoulder 13 of the box. Thelength of this packing recess in the direction of taper and includingthe inner end portions S, S of the cavity is markedly greater than thelength of the packing ring 20 therefor in the'normal initial or freeform of the latter.

It is understood that'in FIG. 2' as well as in FIG. 1 the parts areinstalled in operative position in the pump, and

hence that even in FIG. 2, in which the packing ring 20 is relativelyunstressed as compared with FIG. 1, it is under a degree of axialelongation and radial compression as compared to the wholly free form ofthe ring as it comes from the mold. In other words, in said free formthe ring 20 of the present example measures somewhat less in lengthaxially and a little greater in thickness radially than in the FIG. 2condition wherein it is sufficiently stressed to maintain an effectiveseal at the reduced-diameter rod section there shown, even under thehigh pressure conditions frequently encountered in slush pump operation.

Conversely stated, the wedge ring or tapered packing 20 of the inventionhas a free form and dimensioning such that it is of distinctly lesslength axially than the receiving recess therefor and is of greaterthickness radially than the radial dimension of the annular spaceconstituting such recess, having reference to the maximum exceptableradial dimension of said space at the smallest or most worn diameter ofthe piston rod, such as illus- 'trated at 5 in FIG. 2.

Preferably, in order that the packing 20 may be installed on and removedfrom the piston rod 5 without having to unscrew or disconnect the rodfrom the crosshead, it is longitudinally divided along a line ofseparation 25 seen in FIG. 1 and in more detail in FIG. 4 showing thewedge ring packing element separately, in initial free form. This axialsplit or division line 25 desirably is sinuous, substantially asillustrated and desirably is somewhat inclined to a true radius of thering, providing a lateral lap along the abutted longitudinal edges inaddition to the sinuous curving interlock in the axial direction. Thusthere is no leakage at the split joint 25 of the packing even under arelatively loose status thereof on the rod, such as in FIG. 2, since theconstant wedging action keeps the split joint tight.

The packing in each instance being placed about the rod in the pump isset up into wedging engagement with the inclined wall means 15 of thestufiing box and is locked up in such operative position as by a gland30. The latter is adjustably secured as by nuts 31 threaded on studs 32extending through a lateral flange 33 on the .gland and tapped into theadjacent outer end of the stuf- 'fing box 10. While the gland may engagethe resilient packing 20 direct preferably a fibrous or othersubstantially rigid intermediary collar 34 is interposed between thegland 30 and the resilient wedge ring 20. Such collar 34 desirably isaxially divided, similarly as the wedge ring 20, for lateralinstallation about the rod 5.

In the embodiment of FIGS. 1 and 2 wherein the stufling box inclinedwall such as 16 is provided by an insert wall means or sleeve 15, thusadapting an otherwise generally conventional stufiing box to thepurposes of the invention, a secondary or auxiliary packing desirably isprovided at the inner end portion of such sleeve. For this purpose thesleeve 15 as illustrated is reduced at the inner end 17 to present atapering wall 19. It is disposed at a generally similar small acuteangle to the rod axis as is the inclined wall 16 already described,being shown as parallel with the latter, at an angle of approximately 11to the rod axis.

This inclined wall formation 19 gives to the insert sleeve 15 a generalshallow Z-form in cross-section and defines with the bore 14 and annularshoulder 13 of the stufling box an auxiliary tapering packing recess orcavity R having the taper reversed to that of the described packingrecess for the wedge-ring 20. The auxiliary packing recess R contains aconformably shaped and dimensioned rubberous or other resilient packingring 28. Here again such packing ring 28, which may be longitudinallydivided for mounting purposes, has a normal or initial free axial lengthless than that of the recess R and a radial thickness in the free formsuch that when installed as in FIGS. 1 and 2 it is radiatly compressedand axially elongated,

In the modification f0 FIG. 3 all parts not otherwise mentioned may bethe same as already described and accordingly have the same referencenumerals, including particularly the wedge packing ring 20. In thisinstance the stufling box is cast, machined or otherwise formed to carrythe inclined wall means of the box bore as an integral portion of thebox. The low angle of inclination may be the same as in the previousexample, i.e. in the range of about 8 to 15 to the rod axis. Likewisethe axial and radial dimensioning of the box bore and of the wedgepacking ring 20 relative to each other are as already described inconnection with FIGS. 1 and 2. Thus the inwardly tapering cavity withinthe integral inclined-wall bore of the stufiing box 110 has a length inthe axial direction greater than that of the packing 20 in the free formof the latter, as seen in FIG. 3 at the recess inner end portions S andS' respectively with tapering and with substantially cylindricalcircumferential walls. In other words the integral inclined wall 115 ofthe stuffing box extends at S somewhat beyond the inner end of the wedgering 15 and merges into a substantially cylindrical bore terminal at S.

As in the previous example the installed packing 20 is locked up by agland desirably having an intermediary fibrous or other collar 34between it and the resilient wedge ring 20. While the anchoring of thestuffing box 110 upon the pump cylinder wall 6 and the ad justablesecurement of the gland may be provided for in any convenient manner,FIG. 3 shows for the purpose a series of threaded studs 112' tapped intothe pump cylinder wall and extending commonly through the stufling boxexternal flange 112 and the lateral flange 133 of the gland and eachreceiving a pair of lock-up nuts 113, 114 individually engaging therespective flanges.

The invention is not limited to the particular embodiments thereofillustrated and described herein, its scope being set forth in thefollowing claim.

I claim:

A piston rod packing assembly for a reciprocating piston slush pumphaving a cylinder with an end wall for piston rod entry, said assemblycomprising a rod stuffing box on said wall having a generallycylindrical body with inner and outer ends and a central bore of adiameter substantially greater than the piston rod diameter,

an external mounting flange at the outer body end and an internalannular shoulder at the inner body end with a central aperture affordingfree rod passage,

the packing assembly being characterized by internal circumferentialWall means at the bore of the stuffing box presenting an elongatesurface gradually tapering axially toward the annular inner end shoulderof the box at an acute angle to the axis of the rod,

said tapering wall means along with the circumferential wall of theouter portion of the box bore defining around the rod a tapering annularpacking recess,

a resilient sleeve-like wedge-form packing having a central axialcylindrical bore for receiving and surrounding the rod,

said packing being of circular cross-section at all transverse planesalong it and having a longitudinal crosssectional shape taperingsimilarly to that of the recess with a free axial length less than thatof the recess and a free radial dimension at all points along thepacking greater than that of the recess at the corresponding pointtherealong with reference to the installed position of the packing, saidexcess radial dimension of the packing being greater than maximumexpected variation in diameter of the rod under operative wear,

and gland means for locking up the packing in the recess in such mannerthat by reason of the relative shape and dimension of the packing and ofthe recess and the expansion-contraction flow capacity of the packing anautomatic self-adjusting action of expansion and contraction axially andradially is accorded to the packing as appropriate to maintain a sealabout the rod over varying diameters thereof within the packing,

ing packing recess, and a conformably positioned wedge-section resilientpacking ring in said recess and of a free length axially less than therecess length.

References Cited in the file of this patent and the stuffing box borebeing formed with a standard UNITED STATES PATENTS uniform diameterthroughout the length thereof and the tapering wall means in thestuffing box being 863619 Marten 1907 presented by a separately formedinsert sleeve fitted 1 IOOOSQO Belch 1911 into the stufiing box bore,which insert sleeve has a 1320567 Nawn 1919 longitudinally inwardlyinclined circumferential wall 52 5 5 'f ggy' g at the inner end portiondefining an oppositely taper 2,892,643 Moseley June 30 1959 2,896,980Dicky July 28, 1959

